[Discuss-gnuradio] "video" transmitter

From:

Matthew Kaufman

Subject:

[Discuss-gnuradio] "video" transmitter

Date:

Mon, 2 Feb 2004 16:50:40 -0800

Inspired by the FCC proceedings regarding regulation of D/A converters, I
spent this morning writing software, the idea of which may be of interest to
this group.
Runs under Windows (why? Because that maximizes the number of preinstalled
demo platforms), turns your computer into a radio transmitter. Using the
data contained in a .wav file, modulates your video card as an AM or FM
transmitter by stuffing bits rapidly into the framebuffer (triple-buffered,
uses DirectX/DirectDraw). No real UI yet, just a prototype to prove that it
can be done (which it can, albeit somewhat crudely and with audible
artifacts from vertical blanking). My 1200 MHz K7 machine can do AM and FM
audio at 5-7 MHz no problem (using 640x480x60 Hz), and test tones (can't
update the buffer fast enough for good sounding live audio) all the way up
into the FM broadcast band (1600x1200x90 Hz gets a decently high dot clock)
If, for some reason, someone wanted to prove a point about why regulating
DACs is silly given that every computer with VGA or better video can be a
transmitter, drop me a note and we can put together something that's
demoable.
Matthew Kaufman
address@hidden